/Engine/Source/Runtime/Engine/Classes/GameFramework/CharacterMovementComponent.h
Used during SimulateMovement for proxies, this computes a new value for Acceleration before running proxy simulation. The base implementation simply derives a value from the normalized Velocity value, which may help animations that want some indication of the direction of movement. Proxies don't implement predictive acceleration by default so this value is not used for the actual simulation.
virtual void UpdateProxyAcceleration()